Carboxyl containing polymers, homopolymers, or copolymers with other vinylidene monomers, of unsaturated polymerizable carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid and the like, are useful thickening agents. These polymer acids often are cross-linked with small amounts of cross-linking agents. These materials are usually prepared by polymerization of the acid with a free radical catalyst in an organic medium in a closed vessel with stirring. During the course of such polymerizations, shortly after initiation of polymerization, polymer begins to precipitate from the solution as it is formed and flocculates and forms aggregates. The precipitated polymer forms a slurry in the solvent which often becomes extremely thick and results in ineffective mixing, poor heat transfer, and limits the total solids, i.e., polymer yield, that can be obtained in production equipment. The total solids of such slurries usually is in the range of about 8 to 17 weight percent. Higher yields are desirable.
U.S. Pat. No. 4,375,533 discloses a method for polymerizing olefinically unsaturated carboxylic acids in an organic media in the presence of a catalyst and a surface active agent having an HLB value of less than 10 to reduce the polymer build-up, improve heat transfer, and provide products having improved drying properties and less residual solvent in the dry polymer. However, polymerizations in benzene are generally limited to lower total solids slurries to avoid high slurry viscosity because of excessive flocculation.